Many mechanical devices, other devices that include mechanical components, as well as other types of devices, are capable of operation in any of various states of a plurality of operational states. The allowable state transitions define the allowable state changes that the device is permitted to undergo. The permitted state changes and the permitted states define operation of the device.
A vehicular automatic transmission assembly is exemplary of a device can be represented by operational states and state transitions therebetween. The operational states include, for instance, operational states, and sub-states, associated with the gear positionings of the transmission. The operational states of the vehicular transmission also include states into which the transmission is required to transition in the event of a fault condition. The transition is dependent, not only upon the initial state, but also the type of fault condition. If the fault condition is severe, the transition is to a state that limits further deleterious operation. Conversely, if the fault is minor, the transition is to a state that does not affect continued operation. In other words, the state into which the device is caused to transition responsive to the fault condition is dependent upon the severity of the fault condition.
A vehicular, automatic transmission assembly is conventionally controlled by control apparatus that includes a set of valves. Appropriate closing and opening of specific valves are determinative of the gear positioning of the transmission. Monitoring of the transmission valves is carried out through use of pressure sensors through sensing of pressure levels at locations of the transmission assembly. Sensed pressures are indicative, for instance, of the actual positionings of the valves.
Transmission assemblies are constructed and controlled in manners to minimize safety consequences in the event of occurrence of any of various single points of failure in the transmission assembly and its operation. In the event of occurrence of a fault, the controller of the transmission assembly, such as through operation of pre-determined algorithms, limit operation of the transmission assembly to safe operations so that the vehicle is not damaged and safety is not compromised. While the controller controls the automatic transmission assembly operation to ensure best safe operation, both of the vehicle and to limit damage to the transmission assembly, competitive, and other, pressures compel manufacturers to limit the vehicular operator's exposure to the fault and associated remedies to the fault so as not to cause creation of a negative perception of the transmission assembly. By way example, in the event that a particular clutch control valve fails, a diagnostics algorithm of the transmission controller determines what remedial action to take. For instance, available, remedial actions responsive to the clutch control valve failure includes the shutting down of the vehicle, forcing the vehicle to travel at a reduced speed, or merely setting of an annunciation light. The selection is made, of the available remediations, of the least-invasive, but safe, option.
While control schemes for transmission assemblies and failure-mode analysis thereof, are known and utilized, analysis and controls generally have not fully considered the ramifications and safety impacts of multiple fault occurrences. That is to say, successive faults, or at least one fault subsequent to a first fault occurrence, have generally not been fully analyzed. Ramifications of the subsequent fault occurrences are sometimes therefore not properly controlled in an optimal manner. An analysis would require the determination of all possible permutations of primary faults, remedial actions, subsequent operations, and secondary faults. A very large number of permutations, each requiring consideration, might result. And, if manually evaluated, the evaluations might well be error-prone. And, with each change in remediation operation, the entire analysis might well need to be re-performed. As a result, analysis of the multiple fault occurrence has, to date, generally not been made. If a manner could be provided by which better to analyze multiple fault occurrence of a multiple-state device, improved selection of remediation would be facilitated.
It is in light of this background information related to multi-state devices, that the significant improvements of the present invention have evolved.